Gaudipluma, Artal, Pedro, Van Bakel, Barry W. M., Fraaije, René H. B. & Jagt, John W. M., 2013

Artal, Pedro, Van Bakel, Barry W. M., Fraaije, René H. B. & Jagt, John W. M., 2013, New retroplumid crabs (Crustacea, Brachyura, Retroplumidae Gill, 1894) from the Eocene of Huesca (Aragón, Spain), Zootaxa 3652 (3), pp. 343-352 : 348-351

Gaudipluma n. gen.

Type species. Gaudipluma bacamortensis n. gen., n. sp.

Diagnosis. Carapace large; subrectangular, wider than long, maximum width posteriorly; carapace strongly compressed dorso-ventrally; orbits large, supraorbital margins markedly sinuous; front narrow, relatively long; lateral margins arched, with 2 marked raised lateral nodes; posterior margin convex, wider than orbitofrontal margin; dorsal surface flat in both directions, with 3 subtle, low ridges; thoracic sternum with sternites 3, 4 trapezoidal, sternites 5–7 subrectangular, sternites 6, 7 with prominent median line; sternite 8 inclined, reduced; vulvae subcircular, at extremities of sutures 5/6; male, female abdomens weakly differentiated, narrow; chelipeds subequal; P2–P4 long, with numerous spines; P5 conspicuously reduced; dorsal surface with numerous large pits.

Etymology. In honour of the Catalan architect Antoni Gaudí (1852–1926), in allusion to the shape and ornament of the new taxon which is defined by sinuous lines, reminiscent of his works, plus the ending - pluma, which refers to the main character of the family.

Remarks. The new genus can be differentiated from all others genera in the family Retroplumidae (see De Grave et al. 2009: 44) by a few unique dorsal and ventral characters. The dorsal ridges are fairly attenuated, lateral margins have two conspicuous lateral nodes, male and female abdomens are particularly narrow, the male abdominal segment 6 is long, sternite 7 is unusually large for the family, and distinctly long. Distinguishing features also include a dorsal surface which is densely covered by large pits and P2–P4 with numerous spines, characters never seen in any other retroplumid genera.

Gaudipluma bacamortensis n. sp. ( Figs. 3–4 )

Diagnosis. As for genus.

Etymology. From Bacamorta, the name of the village from where the material originates.

Material examined. MGSB75283, holotype; MGSB75284, 75285a, b and 75286a, b, paratypes; MAB k. 3282–3283, paratypes, all from the vicinity of Bacamorta (Huesca), of early Eocene (Ypresian) age. In the holotype, the maximum carapace width and length (in millimetres) are 39 and 30, respectively.

Description. Carapace large (maximum carapace width about 40 mm); subrectangular in outline; wider than long, widest posteriorly, at level of metabranchial region. Dorsal surface flat in both directions, densely covered by large pits. Orbits large, supraorbital margins sinuous, median sinus projected anteriorly; supraorbital margins terminating in long outer-orbital spines. Front slender, directed anteriorly, relatively long. Lateral carapace margins broadly arched, with 2 conspicuously raised nodes, the first at level of epibranchial region, the second at metabranchial region; posterior margin convex, wider than orbitofrontal margin. Dorsal carapace surface crossed by 3 subtle ridges; anterior ridge continuous, sinuous; median ridge inclined (oblique), interrupted by gastric grooves; posterior ridge continuous. Mesobranchial region subcircular, bounded by subtle grooves. Epibranchial regions slightly swollen, inclined (oblique), interrupted by shallow gastric grooves. Cardiac region weakly defined, slightly raised, forming continuous faint ridge with swollen metabranchial region. Intestinal region depressed. Buccal frame large, subrectangular, mxp3 with large, robust endopodite, narrow exopodite. Thoracic sternum wider than long, sternites 1, 2 subtriangular, small, sternites 3, 4 subtrapezoidal; strong, notable notch between sternites 3, 4; sternite 4 with conspicuous lateral projection; sternites 5–7 subrectangular, wide; sternite 7 longer than 5, 6; sternites 6, 7 with prominent median line; sternite 8 inclined, conspicuously reduced; vulvae subcircular, at extremities of sutures 5/6. Male, female abdomens narrow, sexual dimorphism weak, telson short, small in both sexes; female abdomen subelliptical to subtriangular, with rounded lateral margins, all segments separated; male abdomen subtriangular, with straight, inclined lateral margins; abdominal segment 6 conspicuously long, with clear lateral extensions; male abdominal segments 3–5 fused. Abdominal holding mechanism clearly indicated by lateral projections in sternite 5, lateral extensions of abdominal segment 6. Female vulvae at extremity of suture 5/6 ( Fig. 4 F). P5 subequal, dactyli with numerous small denticles. P2–P4 long, flattened dorso-ventrally, lateral sides with numerous spines. P5 conspicuously reduced (Fig. 34D, E). Dorsal carapace surface densely covered by large pits.

Remarks. The main features of Gaudipluma bacamortensis n. gen., n. sp. match those attributed to other retroplumids (de Saint Laurent 1989: 111–112). Diagnostic features of the new taxon include the general shape of the carapace, large orbits with sinuous margins, narrow front, general shape of the thoracic sternum, with subtrapezoidal sternites 3, 4, rectangular sternites 5–7, an inclined and reduced sternite 8, female vulvae at the extremity of sutures 5/6, P2–P4 long and flattened; P5 conspicuously reduced ( Fig. 4 D, E).

The similarly sized Retrocypoda almelai has a different dorsal surface, with more numerous and better defined dorsal ridges, much wider abdomens, with marked sexual dimorphism, a shorter abdominal segment 6 and longer telson (Via 1969: fig. 41). The female abdomen in Retrocypoda is conspicuously large, occupying a large portion of the ventral surface (Via 1969: pl. 38, fig. 4b). Similar features are seen in Retropluma (see Beschin et al. 1996) as far as male and female abdomens are concerned. The dorsal carapace surface in Retropluma has more strongly marked, acute ridges.

The male and female abdomens of Gaudipluma n. gen. are markedly narrow, and sexual dimorphism is weak. The male abdominal segment 6 is unusually long. The male and female telsons are short in the new genus. Serrablopluma n. gen., Loerentheya and Loerenthopluma all differ mainly in carapace size (smaller), general outline, the construction of the orbits, and all the specific features indicated in the discussion of Serrablopluma n. gen. The female abdomen in Serrablopluma n. gen., Loerenthopluma and Retrocypoda is fairly broad, with distinct sexual dimorphism (see Beschin et al. 1996).

Costacopluma is characterised by a wide geographical distribution ( America, Africa) and a long stratigraphic range (Coniacian–Eocene; see Beschin et al. 1996; Schweitzer et al. 2010). The ten species currently assigned to this genus exhibit a wide range of morphological features, with variable carapace sizes and shapes (subcircular to subelliptical to widely sub-rectangular or elongate). The main distinguishing features of Costacopluma are the stronger dorsal carapace areolation, shorter orbitofrontal margins, wider abdomens and more accentuated sexual dimorphism. The dorsal surfaces of the carapace are more convex and marginal angles are more rounded. The dorsal carapace regions are clearly separated; moreover, the front is much wider and the orbitofrontal margins much shorter (Schweitzer et al. 2003: fig. 16).

Figures

FIGURE 3. Gaudipluma bacamortensis n. gen., n. sp., MGSB 75284 (paratype, female); A, dorsal view; B, ventral view. MGSB 75283 (holotype, male); C, dorsal view (note spines of P 2 – P 4); D, ventral view. MAB k. 3282 (paratype, female); E, dorsal view (note the long, narrow front). All are from the lower Eocene (Ypresian) of the vicinity of Bacamorta (Huesca, northeast Spain). Scale bars equal 10 mm.

FIGURE 4. Gaudipluma bacamortensis n. gen., n. sp., MGS 75285 a (paratype, male); A, ventral view. MGSB 75285 b (paratype, female); B, ventral view, detail of vulvae. MAB k. 3283 (paratype, female); C, ventral view. MGSB 75286 a (paratype, female); D, ventral view; E, details of large sternite 7, reduced sternite 8, reduced P 5 coxa, and P 5 merus; F, details of vulvae at extremities of sutures 5 / 6. All are from the lower Eocene (Ypresian) of the vicinity of Bacamorta (Huesca, northeast Spain). Scale bars equal 10 mm (A – D), 5 mm (E – F). V, vulva; ml, median line; 4 / 5, 5 / 6, 6 / 7, 7 / 8, thoracic sternal suture 4 / 5, 5 / 6, 6 / 7, 7 / 8; St 4, St 5, St 6, St 7, St 8, thoracic sternites 4, 5, 6, 7, 8; cx 2, cx 3, cx 4, cx 5, P 2, P 3, P 4, P 5 coxae; mP 5, P 5 merus.